Digging deep for Africa's renewable energy

Heat from the centre of the Earth — known as geothermal energy — can be used to create a clean and renewable source of electricity.

The energy is harnessed by drilling wells to depths where temperatures reach 345 degrees Celsius. Water pumped into the wells turns into steam, which powers turbines to create electricity.

Several African countries have geothermal resources, but lack the money and infrastructure to use them, reports Ishbel Matheson in this article. Kenya, however, has made some progress. It started using geothermal energy in the early 1980s and now has the continent's largest geothermal power plant at Ol Karia.

The energy source proved its worth when drought struck in 2001. Previously the government had favoured generating electricity from hydroelectric power stations. But as the reservoirs behind the dams dried up, so did the electricity supply.

The year after the drought, work began on a second geothermal power plant at Ol Karia, and a third will be ready by 2010.

But the initial cost of building these power plants is high as it is impossible to predict the best place to drill; the only real way is trial and error. This unpredictability makes it a high-risk investment.

The United Nations Environment Programme is trying to attract private investors to encourage more African countries to use the planet's heat to help power their development.